The octopus, as labeled, stands for the Standard Oil Company. The people in the foreground (If I remember correctly) represent Congress. However, they may represent the owners of smaller oil companies. the Capitol Building shows that the members of congress and the senate were going to do nothing against the company due to the company already having a firm grasp on it (having bribed those people into doing what it wanted). the ships in the background represent the company going overseas to attempt to monopolize the world.